Being a bit of an alt-oholic I have had the chance to look around and find a few leveling guides to help break up the monotany and make things more fun. My criteria for each guide is pretty simple. The guide needs to be free, minimize any mindless grinding, be current and easy to follow.
Here are my favorite guides.
On the Horde side I began both Tandani and Finegas in their home starting areas, Troll and Tauren respectively.
Once they hit level 10 I moved them out to the Ghostlands where I use Snowflake's Guide to the Ghostlands (12-21). My reasoning behind going to the Ghostlands lies in the idea that the new content quests are grouped together for speedier leveling, and the gear is better. That and I'll be spending plenty of time in The Barrens anyhow, I'd like to break up the scenery a bit.
At level 20 its off to The Barrens using Jame's Horde Leveling Guide; which is divided up into six chapters that will take you to level 65.
For the Alliance Characters I would recommend the same kind of pattern. First do all the quests in your starting areas and then head over to the Bloodymist Isle to do your 13-20 level quests there. I didn't use a guide for the area as it was still very new when I went through it. My thinking is the same though. The newer content is better streamlined and has better rewards. You also get a little ticker tape parade at the end that had me a little misty eyed.
From 20 - 30 there is Youri's guide which acts as a prequal for Jame's Alliance Leveling Guide which is the guide that I prefer. This guide is divided into five chapters that will take you all the way to 70.
For tradeskill leveling I prefer to use the crafting guides put together by the folks over at Lootables. These guides are current and concise and they utalize drop down windows rather than putting everything on one long web page. Another great feature that they provide is a shopping list for each tradeskill.
I like to print the shopping list out and have it sitting next to my computer to reference while on my back character. Since I prefer to have gathering trades until level 40 or later I can be stashing away what I need for the profession grind, and then selling off any extra.
Fishing and Cooking
These two skills go hand in hand. I found a great leveling guide on WoWWiki that will tell you what fish you need, and where to fish them. then its a single push of a button and a cup of tea while your character cooks things up. This guide will take you all the way to level 375 in both skills.
Keeping Things Organized.
I keep things interesting for myself by rotating through my characters. Basically I will play a character's rested level down to zero and then switch. I also bounce between Horde and Alliance with one or two characters doing battle grounds at the top of a bracket.
This keeps things fresh but can be a little confusing. To keep things straight I have an index card for each character that I will make some notes on. That way I know right were I am when that character is up for its turn playing.